Polysaccharide-based thermoplastic material, process for preparing the same and method of use thereof

ABSTRACT

The present invention relates to novel thermoplastic materials based on polysaccharide ethers which are simultaneously substituted by carboxylic acid ester groups and carbamate groups, together with mixtures of such derivatives with low molecular weight aliphatic urea derivatives.

The present invention relates to novel thermoplastic materials based onpolysaccharide ethers which are simultaneously substituted by carboxylicacid ester groups and carbamate groups, together with mixtures of suchderivatives with low molecular weight aliphatic urea derivatives.

The invention additionally relates to the production of such derivativesand mixtures of polysaccharide ethers and aliphatic or aromaticcarboxylic acids or carboxylic acid derivatives and aliphaticmonoisocyanates in a suitable solvent. After removal of the solvents,the materials according to the invention are preferably processed asthermoplastic materials by injection moulding or extrusion. Mouldedarticles, fibres, films and also foams or coatings may be produced.

It is known that melt processable materials may be produced frompolysaccharides, in particular from starches or celluloses, byesterification or etherification of the free hydroxyl groups when thereaction is performed homogeneously (cf Encyclopedia of Polymer Scienceand Technology Vol. 3, 1985).

Thermoplastic materials are also obtained, for example according to EP626 392, by esterification of polysaccharide hydroxyalkyl ethers.

JP 142938 and Macromolecules 18, 1985, 1746-1752 describe the reactionof cellulose ethers with acid chlorides or with carboxylic acidanhydrides.

J. Appl. Polym. Sci. 52, 1994, 755-761 and J. Env. Polym. Degr. 3, 1995,115-118 describe the production of thermoplastic cellulose esters fromcellulose and long chain unsaturated fatty acid esters in pyridine/DMF.

The melt processability of polysaccharide derivatives is dependent onthe average degree of substitution of the anhydroglucose repeat unit,abbreviated below as DS, which may amount for example to at leastapproximately 2.0 in the case of thermoplastic aliphatic cellulose esterderivatives.

For melt processing, auxiliary substances, in particular plasticisers,which reduce the viscosity of the material to be softened, have to beadded to these polysaccharide derivatives (F. Muller, Ch. Leuschke inBecker/Braun Kunststoff-Handbuch Vol. 3/1, Hanser Verlag Munich 1992).At elevated temperatures >220° C., it is possible to observedecomposition and discolouration of polysaccharide derivatives.

While etherification is conventionally carried out by reacting alkalicellulose with epoxides, such as for example ethylene oxide or propyleneoxide, in an inert suspending agent, esterification is conventionallycarried out in a solution process using acids as the solvent. In such aninstance, the swelling process also serves to activate the cellulose(Encyclopedia of Polymer Science and Technology Vol. 3, 1985).

Synthesis of the known polysaccharide carboxylic and dicarboxylic acidhalf esters is effected in pyridine or acetic acid with basic salts suchas for example sodium acetate as the catalyst (J. Env. Pol. Degr. 3,1995, 115-119). The products may be liberated from these solvents onlywith considerable effort. Because they accelerate corrosion, thesesolvents require specially designed installations for synthesis thereof.Syntheses carried out in standard organic solvents would be advantageousin this respect.

Economic derivatisation of celluloses using acid derivatives with adegree of substitution <<3 and homogeneous random distribution of theacid derivatives has hitherto required complete substitution of thecellulose (DS approx. 3.0) with subsequent partial hydrolysis (U.S. Pat.No. 1,984,147, U.S. Pat. No. 2,129,052, U.S. Pat. No. 5,478,386).

Thermoplastic cellulose derivatives with DS <3.0 and homogeneous randomsubstituent distribution have not hitherto been economically directlyavailable. This is primarily because of the poor, incomplete solubilityof partially substituted celluloses in suitable organic solvents.

Likewise, it is possible to achieve uniform reaction of polysaccharideswith substituted isocyanates or substituted isothiocyanates only in thecase of good accessibility of the cellulose chains in homogeneoussolution or in solvents with a very strong swelling action.

Acta Polymerica 32, 1981, 172-176 describes how dry cellulose reacts inan unsatisfactory manner with isocyanates in the absence of solvents andother catalysts. Reactions in solvents which are not in a position atleast to initiate swelling of the cellulose do not produce satisfactoryreactions with the cellulose (Ang. Chem., 59, 1947, 257-288).

B. Polym. J., 18, 1986, 259-262 describes the reaction of lignocellulosewith alkyl monoisocyanates. Urethane formation remains restricted to thesurface of the polysaccharide fibres.

DE 23 58 808 describes the reaction with long chain mono- anddiisocyanates restricted to the surface of cellulose powder.

In “Neueste Fortschritte und Verfahren in der chemischen Technologie derTextilfasern”, Birkhäuser Verlag, Stuttgart, 1957, L. Disserens providesa summary of the reactions, restricted to the surface, of textile fibresmono- and diisocyanates. In this context, long chain alkyl isocyanatesare preferably used for the purpose of hydrophobising textile material.GB 467 992 describes the heterogeneous reaction with isocyanates oftextile fibres previously reacted with alkylene oxides. In the case ofthe reaction carried out in benzin, however, no significant swelling ofthe cellulose occurs.

Average degrees of conversion of cellulose with isocyanates areobtained, with solvents and catalysts, in particular when the celluloseis initially present in a swollen state. This may be achieved by using asuitable solvent or by using a derivative of cellulose or apolysaccharide together with a suitable solvent. Formation of theurethane bond may also be effected by a subsequent baking process (Cell.Chem. Technol. 1, 1967, 23-32).

Swelling of the cellulose may be achieved by initiating said swelling inwater, which is subsequently replaced by a polar aprotic solvent.

Alternatively, direct use may also be made of solvents with a strongswelling or dissolving action in relation to cellulose, such as DMAc,DMSO, DMAc/LiCl or DMSO/formaldehyde mixtures (U.S. Pat. No. 4,129,451,U.S. Pat. No. 4,129,640, U.S. Pat. No. 4,097,666). Solvent systems aresummarised in Nevell and Zeronian: Cellulose chemistry and itsapplications, Wiley, N.Y. 1985, Acta. Polym. 36 (1985), 697-698 andPolymer news 15, (1990), 170-175.

Examples of other systems described as having a good swelling ordissolving action are, for example, morpholine/piperidine mixtures (J.Appl. Polym. Sci., 22, (1978), 1243-1253) together with amine-N-oxides(Acta Polymerica, 39, (1998), 710-714, U.S. Pat. No. 3,508,941) andmetal cation/solvent systems such as Cu/NH3 or Cd/ethylene diamine(Polymer 31, (1990), 348-352).

The reaction of phenyl isocyanate with cellulose inDMSO/paraformaldehyde mixtures is described in J. Appl. Pol. Sci. 27,(1982), 673-685, J. Appl. Pol. Sci. 42, (1991), 821-827 and in Nevelland Zeronian: Cellulose chemistry and its applications, Wiley, N.Y.1985.

High degrees of conversion are promoted, in particular, by the additionof catalysts, by a correspondingly long reaction period or by elevatedtemperature. On the other hand, where DMAc, DMSO or DMF is used as aswelling agent or solvent, the formation of isocyanurates is catalysedwith amines (Eur. Polym. J., 26 (11)(1990) 1217-1220).

The patents and publications listed below describe the reaction ofsoluble cellulose acetate with degrees of substitution DS<3.0 withisocyanates, isocyanate prepolymers or isocyanate-functionalisedpolymers or oligomers in homogeneous solution. After formation of theurethane, the acetate groups may be saponified and urethane derivativesof the unsubstituted cellulose may be isolated:

J. Macromol. Sci. Chem A 16 (1981) 473, Polym. Prepr. Am. Chem. Soc.Div. Poly. Chem. 20 (1979) 574. J.Poly. Sci. Polym.Lett.ed. 111(12)(1973) 731-735, Macromol. Synth. 7 101-105, Polymer 21 (1980) 648-650,Polym. Prepr. Am. Chem. Soc. Div. Poly. Chem.3 (1990) 642, U.S. Pat. No.395,028).

The reaction of polysaccharide derivatives with aliphatic isocyanates toform thermoplastic materials is described in DE 19 613 990. However, theeconomic viability of the process requires improvement.

Polysaccharide ethers which have been modified simultaneously bycarbamate and ester groups and may thereby be melt processed are notdescribed.

DE 43 38 152 describes the production of aliphatic carbamates fromstarch and starch acetates. Starch ethers are not described in thisconnection. In comparison with cellulose derivatives, starch derivativesexhibit only inadequate mechanical properties. Moreover, in comparisonwith cellulose, starch requires fundamentally different synthesisconditions in suitable organic solvents, such that knowledge acquired inrelation to starch derivatives cannot be applied to cellulosederivatives or can only be applied thereto to a limited extent.

The object of the invention is to achieve economic reaction conditionsfor the reaction of polysaccharide ethers, particularly preferably thosefrom cellulose, with isocyanates and carboxylic acids or carboxylic acidderivatives, such that low to high degrees of conversion are obtainedand melt processing is possible.

For this purpose, it was hitherto necessary, in particular, to carry outthe reaction under homogeneous conditions, i.e. by dissolution of thepolysaccharide derivative in solvents.

It has surprisingly been found that polysaccharide ethers, andparticularly preferably cellulose alkyl ethers which are initiallyneither soluble nor readily swellable in the solvents used according tothe invention, are dissolved or begin to swell markedly during thereaction with alkyl monoisocyanates and that, directly subsequent to thereaction with the alkyl isocyanates, esterification with aromatic oraliphatic mono- or dicarboxylic acids may occur, which alternativelyproduces low to high degrees of conversion and results in homogeneousrandom distribution of the ester and carbamate groups along the maincellulose chain.

Furthermore, it has surprisingly been found that the main products X ofthis process according to the invention may be melt processable and inparticular the by-products Y of the process according to the inventionimprove the melt processability of the products according to theinvention.

In addition, it has surprisingly been found that, in contrast to theabove-described prior art, melt processing of the derivatives accordingto the invention is also possible at low degrees of substitution<DS=2.0and, moreover, does not necessarily require the addition of aplasticiser, since the viscosity of the softened material issufficiently low for melt processing. The addition of plasticisers ispossible nonetheless and improves the mechanical properties of thematerial processed.

The present invention relates to uniformly substituted polysaccharidederivatives of the general structure

polysaccharide-O-R

in which polysaccharide-O represents a substituted or unsubstitutedpolysaccharide unit and R is a substituent of a polysaccharide-OH grouphaving either the structure

R=—A—B—

or the structure

R=—A—C—

or the structure

R=—B—

or the structure

R=—C—

in which A is a linear polyether chain of the following structure:

A=(—D—O—)n

in which D denotes a linear aliphatic branched or unbranched chain of 2to 12 C atoms, O represents an oxygen atom and n is a number equal to orgreater than 1, and

B represents a substituted carbamic acid of the structure

in which E denotes a linear or branched aliphatic chain of 1 to 18 Catoms,

C represents a carboxylic acid ester of the structure

in which F denotes a linear aliphatic, saturated or unsaturated,branched or unbranched chain of 2 to 22 C atoms.

This surprising result of the procedure according to the invention wasnot foreseeable for the person skilled in the art. The person skilled inthe art would have expected it to be necessary to achieve a high overalldegree of substitution for melt processing and a homogeneous randomsubstituent distribution, and that for this purpose a homogeneousreaction in solution and optionally the addition of a plasticiser wouldbe necessary.

The combination of substituents in particular, together with the processaccording to the invention, produce the surprising result, however. Inaddition, it would have been expected that the by-products Y woulddecompose during subsequent melt processing and form troublesome gaseousdecomposition products.

The new compounds A correspond to the general structure

polysaccharide-O-R

in which polysaccharide-O represents a repeat unit of a polysaccharideor polysaccharide ether and R is a substituent group, which is bonded tothe polysaccharide derivative via an oxygen atom.

These substituents R consist of a random mixture of at least 2 or moresubstituents with homogeneous distribution along the main polysaccharidechain. The substituent mixture may consist of unbranched or branched,aliphatic or aromatic mono- or dicarboxylic acid ester groups and ofunbranched or branched aliphatic carbamate groups.

The molar ratio of the components X and the by-products Y is representedby the formula

0.001<Y/(X+Y)<0.3.

It is particularly preferred for the molar ratio Y/(X+Y) to amount to atleast 0.01, in particular 0.05-0.1. If the limit value of 0.3 isexceeded in the above formula, i.e. if the proportion of the by-productsis increased, the product no longer exhibits the mechanical propertiesnecessary for practical application.

The function according to the invention of the by-product Y is onlyobtained if the melt temperature of Y is lower than the processingtemperature.

The invention thus provides melt processable polysaccharideether/ester/carbamate derivatives, characterised in that they may beproduced from polysaccharides, wherein firstly polysaccharide ethers areproduced by etherification, which polysaccharide ethers are then reactedwith isocyanates, optionally in blocked form, and carboxylic acidderivatives to form polysaccharide ether/carbamate/ester derivatives.

In a preferred embodiment, first of all cellulose ethers with averagedegrees of substitution MS per anhydro-glucose unit MS=0-5, preferably0.1 to 5, particularly preferably 0.4-1.5, are produced or used, whereinthe average degree of substitution is dependent on ether substituentsand may be >3.0 in the case of further functionalisable ether groupssuch as, for example, hydroxypropyl ethers of cellulose but may amountonly to a maximum of MS=3.0 in the case of cellulose ether groups whichmay not be further functionalised, such as for example methylcellulose.

In a further preferred embodiment, the average overall degree ofsubstitution, based on the sum of ester and carbamate substituents,relative to the anhydroglucose unit, amounts to DS=0.3-3.0, preferably0.6 to 2.8, particularly preferably 0.5-2.5, wherein the proportion ofcarbamate substituents in the DS=0.3-3.0 amounts to at least 0.2,preferably 0.3-1.0.

The invention also relates to the mixture of the polysaccharideether/ester/carbamate derivatives according to the invention with lowmolecular weight unbranched or branched, symmetrical or asymmetrical,aliphatic dialkyl urea derivatives with chain lengths of from 1-20carbon atoms.

In a preferred embodiment, the molar ratio of the polysaccharideether/ester/carbamate derivatives X according to the invention and thedialkyl urea derivatives Y is represented by the formula0.01<Y/(X+Y)>0.3. The molar ratio Y/(X+Y) particularly preferablyamounts to at least 0.01, very particularly preferably to 0.05-0.1.

The invention further relates to a process for producing suchpolysaccharide ether ester carbamates according to the inventiontogether with mixtures thereof with low molecular weight ureaderivatives, said process being characterised in that first of all thepolysaccharide ether is produced, this then being added to a non-solventwith a suitable catalyst and then converted, using an isocyanate, intothe corresponding carbamate, wherein the polysaccharide ether carbamatesthus obtained, which optionally contain low molecular weight ureaderivatives, are soluble or swell markedly in the solvent or suspendingagent used and are subsequently esterified by the addition of suitableactivated derivatives of carboxylic acids and may then be isolated byprecipitation, evaporation of the solvents or devolatilising extrusion.

In a preferred embodiment, the average overall degree of substitutionbased on the sum of ester and carbamate substituents relative to theanhydroglucose unit amounts to DS=0.3-3.0, particularly preferably0.5-2.5.

In a further preferred embodiment, the molar ratio of the dialkyl ureaderivatives arising during carbamate formation is represented accordingto the invention by the formula 0.01<Y/(X+Y)<0.3 (molar amount ofpolysaccharide ether/ester/carbamate derivatives=X and molar amount ofdialkyl urea derivatives=Y). The molar ratio Y/(X+Y) particularlypreferably amounts to at least 0.01, very particularly preferably to0.05-0.1.

In a preferred embodiment, mono- or difunctional carboxylic acidchlorides, anhydrides or activated esters thereof are used as theactivated aliphatic or aromatic carboxylic acid derivatives. Aliphaticcarboxylic acid anhydrides are particularly preferable.

The polysaccharide ether ester carbamates according to the invention mayoptionally be provided with conventional additives such as, for example,plasticisers, impact resistance modifiers, flame retardants,anti-oxidants, UV protectors, hydrophobising agents, nucleating agentsand/or other agents, together with fillers.

The invention also provides use of the melt processable polysaccharideether/ester/carbamate derivatives according to the invention as athermoplastic material for the production of injection moulded articles,for extrusion, for blow moulding of for example bottles/plant pots andother blow mouldings and for the production of films, fibres, foams andcoatings.

Processing of the materials according to the invention is effected inconventional plastics processing machines such as for example injectionmoulding machines or extruders. In such instances, temperatures of from80-220, preferably 100-200° C. are used.

For the purpose of synthesis, the polysaccharide is optionally activatedusing alkali metal hydroxide solution or ammonium salts, but may also beactivated hydrothermally, using liquid ammonia and/or by ultrasound. Theactivated polysaccharide may be isolated or subjected directly tofurther processing. Before the etherification reaction is begun,optionally present water or solvents is/are removed by solvent scouringor by distillation, and the polysaccharide ether is produced by theaddition of epoxide. Etherification is also possible in the presence ofaqueous alkali metal hydroxide solution.

For further synthesis, an extensively water-free polysaccharide ether(water content <5 wt. %), preferably a cellulose ether such as forexample hydroxypropyl- or hydroxyethylcellulose, is refluxed in asuspending agent, the isocyanate compound being added dropwise after theaddition of a catalyst. The isocyanate reacts with the polysaccharideether in a solid/liquid two-phase reaction in standard suspendingagents. In suspending agents such as dioxane and toluene, the reactionproducts become dissolved during the reaction. This surprisinghomogenisation of the reaction solution ensures that reaction withfurther derivatives may occur in simplified manner. Surprisingly, it ispossible in this way also to obtain homogeneously derivatisedpolysaccharide ether carbamate esters having a low degree ofsubstitution, which may thus be obtained without the need for fullsubstitution and subsequent hydrolysis.

The overall degree of substitution is composed of the individual degreesof substitution for carbamate and carboxylic acid ester and amounts atmost to 3 if further functionalisable ether groups are present, such asfor example in hydroxypropyl ethers of the polysaccharides. In the caseof cellulose ether groups which cannot be further functionalised, suchas for example in methylcellulose, the maximum DS possible is reduced bythe average degree of substitution MS of the polysaccharide ether used.

Isolation of the product may be effected, in the process according tothe invention, by means of, for example precipitation, evaporation ofthe solvent or devolatilising extrusion.

The stoichiometry and the progress of the reaction may be used to adjustwithin broad margins the degree of conversion of the polysaccharidederivative, together with the proportion thereof consisting of carbamateand ester groups. For melt processability of the material, an overalldegree of substitution of over 1.0 is sufficient.

Polysaccharides and polysaccharide derivatives may, at normal pressureand room temperature, contain a low proportion by weight of water. Thesecondary reaction of the isocyanate compounds with water results in theformation of by-products preferably including di- substituted ureas. Theextent to which by-products are formed largely depends on the watercontent of the reaction solution. These by-products exhibit meltingtemperatures <200° C. and result, provided that they are not removedduring working up of the polysaccharide derivatives, in a markedimprovement in the melt processability of the product.

In a further stage, during esterification according to the invention ofthe polysaccharide derivatives with dicarboxylic acid esters, thecarboxyl group, which is still free, of the dicarboxylic acid monoesterthus obtained may be reacted with alkylene oxides. The proportions maybe such that the free carboxylic acids are completely or only partiallyreacted with alkylene oxide. Likewise, the free acid groups may serve asinitiators for polymeric ether synthesis.

If amine was used for activation, it serves as a catalyst during thisreaction stage too. Small amounts of amine may accordingly be added atthis point in the event of alkali activation.

For the purpose of synthesis, industrially obtainable polysaccharides ofany molecular weight, such as for example native and soluble starch ofany provenance, amylose, amylopectin, alginic acids and alginates,carrageenan, chitin, chitosan, dextran, glycogen, guar gum, carob flour,laevosan, pectin, pullulan, xanthan gum and xylan are suitable.Cellulose is particularly preferred.

If polysaccharide ethers, in particular cellulose ethers, are put todirect use, suitable cellulose ethers are methylcellulose,ethylcellulose or benzylcellulose with average degrees of substitutionlower than or equal to 2.5, hydroxyethylcellulose,hydroxypropylcellulose, di-hydroxypropylcellulose,hydroxybutylcellulose, methylhydroxyethylcellulose,methylhydroxypropylcellulose, methylhydroxybutylcellulose,ethylhydroxypropylcellulose, ethylhydroxyethylcellulose,carboxyalkylcellulose, sulfoalkylcellulose, cyanoethylcellulose andmixed ethers thereof. Ethers of the above-mentioned polysaccharides mayalso be used as the polysaccharide component.

Suitable suspending agents or solvents are ketones such as for examplemethylethyl ketone, ethers and cyclic ethers such as for exampledimethoxyethane, dimethoxymethane, dimethyl ether, diethylene glycoldimethyl ether, dioxane and tetrahydrofuran, acetals, hydrocarbons andpolar aprotic compounds such as dimethyl sulfoxide, dimethyl formamide,dimethyl acetamide, N-methyl morpholine, N-methyl pyrrolidone, trialkylphosphate, ethyl acetate and non-polar aprotic solvents such as toluene.Dioxane and toluene are preferred.

Suitable isocyanate compounds include aliphatic linear and branchedmonoisocyanates with a saturated or unsaturated alkyl chain such as forexample methyl isocyanate, ethyl isocyanate, propyl isocyanate,isopropyl isocyanate, butyl isocyanate, pentyl isocyanate, hexylisocyanate, heptyl isocyanate, octyl isocyanate, nonyl isocyanate, decylisocyanate, undecyl isocyanate, dodecyl isocyanate, tetradecylisocyanate, hexadecyl isocyanate, octadecyl isocyanate, thecorresponding isothiocyanates together with any mixtures of theabove-mentioned monoisocyanates and isothiocyanates.

Suitable catalysts for the reaction are amines, in particularstearically inhibited tertiary organic amines such as trimethylamine,triethylamine, tributylamine, tetramethylene diamine, pyridine,N,N-dimethylcyclohexyl diamine, N,N-dimethylbenzylamine,4-pyrilidinopyridine, permethyl diethylene triamine,1,4-diazabicyclo[2.2.2]-octane, 1,8-diazabicyclo[5.4.0]undec-7-ene,1,5-diazabicyclo[4.3.0]non-5-ene together with any mixtures thereof.

Catalysts conventional in polyurethane chemistry are also suitable, suchas for example organotin compounds.

During catalysis, the amount of amine to be used has an effect on thedegree of derivatisation of the polysaccharide. For reaction with thepolysaccharide derivative, the amine is used in a molar ratio to thepolysaccharide of 0.01 to 3, preferably 0.1 to 1.

For formation of the ester substituents according to the invention ofthe polysaccharide derivatives, it is possible to use substituted orunsubstituted, aliphatic or aromatic, branched or unbranched carboxylicacid derivatives, such as for example the corresponding acid chloridesor anhydrides. It is preferable to use the carboxylic acid anhydridessuch as for example acetic anhydride, propionic anhydride, isobutyricanhydride, butyric anhydride, trimethyl acetic anhydride, valericanhydride, hexanoic anhydride, nonanoic anhydride and mixtures thereof.Of these, acetic anhydride, propionic anhydride, isobutyric anhydrideand butyric anhydride are particularly preferred.

Suitable dicarboxylic acid anhydrides are anhydrides of substituted orunsubstituted, aliphatic or aromatic, branched or unbrancheddicarboxylic acid derivatives, preferably their acid chlorides oranhydrides. Use is particularly preferably made of phthalic anhydride,tetrahydrophthalic anhydride, hexahydrophthalic anhydride, maleicanhydride, succinic anhydride, trimellitic anhydride and isatoicanhydride. Also suitable are alkane and alkenyl succinic anhydrides suchas hexyl, hexenyl, octyl, octenyl, nonyl, nonenyl, decyl, decenyl,dodecyl, dodecenyl, tetradecyl, tetradecenyl, hexadecyl, hexadecenyl,octadecyl, octadecenyl, isooctadecyl, isooctadecenyl, eicosyl anddocosyl succinic anhydride.

Suitable epoxides are preferably monoepoxides such as ethylene oxide,propylene oxide, 1,2-epoxybutane, 1,2-epoxyhexane, 1,2-epoxyoctane,1,2-epoxydecane, 1,2-epoxydodecane, 1,2-epoxyhexadecane,1,2-epoxyoctadecane, stearic acid glycidyl ether, epoxybutyl stearate,lauryl glycidyl ether, glycidyl methyl ether, glycidyl ethyl ether,glycidyl propyl ether, glycidyl butyl ether, glycidyl tertiary butylether, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether,butadiene monoxide, glycidol, 3-glycidoxypropyl trimethoxysilane,3-glycidoxy-propyl triethoxysilane, di-N-butylamino-2,3-epoxypropane,diethyl-β,γ-epoxypropyl phosphate, 4-(2,3-epoxypropyl) morpholine,styrene oxide and phenoxypropylene oxide.

The reaction temperature of the polysaccharide derivatives with theisocyanates and carboxylic acid derivatives amounts to from 20 to 150°C., preferably 40-130° C., particularly preferably 60-120° C. Thereaction times amount to from 0.5 to 16 hours, preferably 0.5 to 9hours.

The polysaccharide ester carbamates obtainable by the process accordingto the invention may be melt processed after removal of the solvents andconverted, by conventional processing methods such as extrusion, intoinjection mouldings, films or fibres for example.

The process according to the invention is further characterised in thatby-products, particularly preferably dialkyl ureas, are formed duringthe reaction, depending on the water content of the polysaccharidecomponent. The presence of these by-products in the product improves themelt processability of the cellulose ether urethane derivatives.

The polysaccharide derivatives according to the invention and mixturesthereof with low molecular weight urea derivatives are suitable for theproduction of coatings, fibres, powders, films, foams and mouldedarticles. Their properties may be varied by producing blends of anycomposition with other components, such as polysaccharides andpolysaccharide derivatives or polyurethanes for example. They may alsobe combined-with plasticisers, flame retardants, pigments and auxiliaryprocessing substances such as for example long chain fatty acid amides.In particular, the addition of plasticisers such as for exampletriethylene glycol, aliphatic esters of phthalic acid, adipic acid,azelaic acid, sebacic acid and phosphoric acid, such as for exampledimethyl phthalate, dibutyl phthalate, dibutyl adipate, dioctyl adipate,dibutyl acetate, trichloroethyl phosphate, trichloropropyl phosphate andtributyl phosphate together with lactic acid esters or tartaric acidesters or mixtures of the above-mentioned plasticisers improves meltprocessability and enables processing even at low degrees ofsubstitution such as for example DS=0.5-1.0.

The melt processable moulding compositions according to the inventionmay additionally contain additives capable, for example, of colouring orpigmenting the polymer mixtures, improving their oxidation or lightresistance or reducing their inflammability.

The subject matter of the present invention will be described in moredetail with the aid of the Examples provided.

EXAMPLES ACCORDING TO THE INVENTION

Cellulose ethers used according to the invention, such as for examplethe hydroxypropylcellulose (HPC) used in the following Examples, may beobtained by industrial processes such as are described in, for example,Encyclopedia of polymer science and engineering, Vol 3, 1985, Wiley N.Y.The HPC used in the Examples is distinguished by MS values of 0.4-4.5 ata molecular weight (number average) ranging from 10,000-200,000. HPCshaving MS=0.9, Mw approx. 200,000 were preferably used.

Example 1

5.3 g (0.025 mol) of dried hydroxypropylcellulose is refluxed in 200 gdioxane with 0.0125 mol DBU for 30 minutes. The isocyanate is then addeddropwise and the mixture is stirred with refluxing for two hours.Thereafter, phthalic anhydride, dissolved in 50 g dioxane, is addeddropwise and the mixture is stirred with refluxing for three hours.0.025 mol of propylene oxide is then added dropwise and the mixture isstirred with refluxing for 13 hours. The product is precipitated fromacetone, washed with acetone and dried in a vacuum. In the table below,the amounts used, the yield and the softening temperature of the productare indicated.

n-stearyl isocyanate Phthalic anhydride Propylene oxide Yield ST g/molg/mol g/mol (g) (° C.) 7.3/0.025 7.4/0.05 5.8/0.1 15.5 170

Example 2

5.3 g (0.025 mol) of dried hydroxypropylcellulose MS 0.9 is refluxed in200 g dioxane with 0.0125 triethylamine for 30 minutes. The isocyanateis then added dropwise and the mixture is stirred with refluxing for twohours. Thereafter, phthalic anhydride, dissolved in 50 g dioxane, isadded dropwise and the mixture is stirred with refluxing for threehours. Acetic anhydride is then added dropwise and the mixture isstirred with refluxing for 13 hours. The product is precipitated fromacetone, washed with acetone and dried in a vacuum. In the table below,the amounts used, the yield and the softening temperature of the productare indicated.

n-stearyl isocyanate Phthalic anhydride Acetic anhydride Yield ST g/molg/mol g/mol (g) (° C.) 7.3/0.025 74/0.05 5.1/0.05 11.4 180

Example 3

5.3 g (0.025 mol) of dried hydroxypropylcellulose MS 0.9 is refluxed in200 g dioxane with 0.0125 triethylamine for 30 minutes. The isocyanateis then added dropwise and the mixture is stirred with refluxing for twohours. Thereafter, phthalic anhydride, dissolved in 50 g dioxane, isadded dropwise and the mixture is stirred with refluxing for threehours. Propionic anhydride is then added dropwise and the mixture isstirred with refluxing for 13 hours. The product is precipitated fromacetone, washed with acetone and dried in a vacuum.

In the table below, the amounts used, the yield and the softeningtemperature of the product are indicated.

n-stearyl isocyanate Phthalic anhydride Propionic anhydride Yield STg/mol g/mol g/mol (g) (° C.) 7.3/0.025 7.4/0.05 6.5/0.05 11.8 180

Example 4

5.3 g (0.025 mol) of dried hydroxypropylcellulose MS 0.9 is refluxed in200 g dioxane with 0.2 ml 1,8-diazabicyclo[4.5.0]undec-7-ene for 30minutes. The isocyanate is then added dropwise and the mixture isstirred with refluxing for two hours. Thereafter, propionic anhydride,dissolved in 50 g dioxane, is added dropwise and the mixture is stirredwith refluxing for 13 hours. The product is precipitated from n-hexane,washed with hexane and dried in a vacuum.

In the table below, the amounts used, the yield, the softeningtemperature and the degree of substitution, detected by ¹³C-NMRspectroscopy, of the product are indicated.

Propionic anhydride Yield DS DS ST g/mol (g) Carbamate Propionate (° C.)n-butyl isocyanate g/mol 4a 2.4/0.025 6.5/0.05 6.9 1.0 1.1 200 n-stearylisocyanate g/mol 4b 3.6/0.0125 6.5/0.05 7.3 0.2 1.2 210 4c 7.3/0.0256.5/0.05 11.5 0.5 0.6 180 4d 3.6/0.0125 3.3/0.025 10.1 total 1.2 195 4e7.3/0.025 3.3/0.025 12.6 total 1.0 180

Mechanical testing according to DIN 53 457 and ISO 180-1C results in thefollowing mechanical properties:

(The values indicated are the equivalents of the isocyanates andanhydrides used in the reaction based on the repeat unit of the HPC)

Modulus n-stearyl Propionic of Tensile Elongation isocyanate anhydrideST elasticity strength at break equivalents equivalents (° C.) (MPa)(MPa) (%) 4b 0.5 2 210 570 12.2 8.3 4c 1 2 180 650 15.4 6.6 4d 0.5 1 1952340 19.5 0.9 4e 1 1 180 1240 22 2.7

Example 5

5.3 g (0.025 mol) of dried hydroxypropylcellulose MS 0.9 is refluxed in200 g dioxane with 0.2 ml 1,8-diazabicyclo[4.5.0]undec-7-ene for 30minutes. The isocyanate is then added dropwise and the mixture isstirred with refluxing for two hours. Thereafter, butyric anhydride,dissolved in 50 g dioxane, is added dropwise and the mixture is stirredwith refluxing for 13 hours. The product is precipitated from water pH8-9, drawn off, then washed again with water pH 9 and dried in air.

In the table below, the amounts used, the yield, the softeningtemperature and the degree of substitution, detected by ¹³C-NMRspectroscopy, of the product are indicated.

n-stearyl Butyric isocyanate anhydride Yield DS ST g/mol g/mol (g)Carbamate DS Butyrate (° C.) 5a 3.6/0.0125 7.9/0.05 11.54 0.2 1.5 150 5b3.6/0.0125 3.9/0.025 9.9 0.1 1.0 170 5c 7.3/0.025 3.9/0.025 13.5 0.4 0.6180 5d 7.3/0.025 7.9/0.05 15.0 0.5 1.7 150

Example 6

26.7 g (0.125 mol) of dried hydroxypropylcellulose MS 0.9 is refluxed in750 g dioxane with 1 ml 1,8-diazabicyclo[4.5.0]undec-7-ene for 30minutes. The isocyanate is then added dropwise and the mixture isstirred with refluxing for two hours. Thereafter, butyric anhydride,dissolved in 50 g dioxane, is added dropwise and the mixture is stirredwith refluxing for 9 hours. The product is precipitated from water pH8-9 (NH4OH), drawn off, then washed again with water pH 9 and dried inair.

In the table below, the amounts used, the yield, the softeningtemperature and the degree of substitution, detected by ¹³C-NMRspectroscopy, of the product are indicated.

n-stearyl Butyric isocyanate anhydride Yield DS DS ST g/mol g/mol (g)Carbamate Butyrate (° C.) 6a 18.4/0.0625 39.5/0.25 76 0.5 1.2 165 6b18.4/0.0625 59.2/0.375 78 0.5 1.4 165 6c 36.8/0.125 19.7/0.125 68 0.20.3 230 6d 36.8/0.125 39.5/0.250 71 0.3 0.5 190 6e 36.8/0.125 59.2/0.37557 0.4 1.3 180

Example 7

When tested mechanically according to DIN 53 457 and ISO 180-1C, thematerials described in Examples 5 and 6 exhibit the followingproperties:

(The values indicated are the equivalents of the isocyanates andanhydrides used in the reaction based on the repeat unit of the HPC)

Modulus n-stearyl Butyric of Tensile Elongation isocyanate anhydride STelasticity strength at break equivalents equivalents (° C.) (MPa) (MPa)(%) 7a 0.5 1 170 300 6.6 4.9 7b 0.5 2 150 430 11.1 7.9 7c 0.5 2 165 24411.5 10.0 7d 0.5 3 165 104 10.0 35.5 7e 1 1 180 600 12.5 4.4 7f 1 1 230405 8.0 2.9 7g 1 2 190 316 9.4 7.7 7h 1 3 180 279 14.3 33.2

Comparative Examples

The molar amounts given below for polymers and oligomers are based onthe average molecular weights of the ideal repeat units.

Comparative Reaction 1

5.3 g (0.025 mol) of dried hydroxypropylcellulose MS 0.9 is refluxed in200 g dioxane with 0.2 ml 1,8-diazabicyclo[4.5.0]undec-7-ene for 30minutes. Thereafter, the acetic anhydride, dissolved in 50 g dioxane, isadded dropwise and the mixture is stirred with refluxing for 13 hours.The product is precipitated from n-hexane, washed with hexane and driedin a vacuum.

In the table below, the amounts used, the yield, the softeningtemperature and the degree of substitution, detected by ¹³C-NMRspectroscopy, of the product are indicated.

Acetic anhydride Yield DS ST (g)/mol (g) Acetate (° C.) 5.1/0.05 6.8 1.3220 highly viscous opaque

Comparative Reaction 2

5.3 g (0.025 mol) of dried hydroxypropylcellulose MS 0.9 is refluxed in200 g dioxane with 0.2 ml 1,8-diazabicyclo[4.5.0]undec-7-ene for 30minutes. Thereafter, propionic anhydride, dissolved in 50 g dioxane, isadded dropwise and the mixture is stirred with refluxing for 13 hours.The product is precipitated from n-hexane, washed with hexane and driedin a vacuum.

In the table below, the amounts used, the yield, the softeningtemperature and the degree of substitution, detected by ¹³C-NMRspectroscopy, of the product are indicated.

Propionic anhydride Yield DS ST g/mol (g) Propionate (° C.) 6.5/0.05 5.61.4 220 highly viscous opaque

Comparative Reaction 3

5.3 g (0.025 mol) of dried hydroxypropylcellulose MS 0.9 is refluxed in200 g dioxane with 0.2 ml 1,8-diazabicyclo[4.5.0]undec-7-ene for 30minutes. Thereafter, butyric anhydride, dissolved in 50 g dioxane, isadded dropwise and the mixture is stirred with refluxing for 13 hours.The product is precipitated from water pH 8-9, drawn off, then washedagain with water pH 9 and dried in air.

In the table below, the amounts used, the yield, the softeningtemperature and the degree of substitution, detected by ¹³C-NMRspectroscopy, of the product are indicated.

Butyric anhydride Yield DS ST g/mol (g) Butyrate (° C.) 7.9/0.05 7.7 1.5180 highly viscous opaque 3.9/0.025 5.8 0.9 240 decomposition

Comparative Reaction 4

7.1 g (0.025 mol) of plastic acetate DS 2.0 (acetate 53%) is refluxedwith 1,8-diazabicyclo[4.5.0]undec-7-ene for 30 minutes in 200 g dioxane.The isocyanate, dissolved in 50 g dioxane, is then added dropwise andthe mixture is stirred with refluxing for two hours. The product isprecipitated from n-hexane, washed with hexane and dried.

In the table below, the amounts used, the yield, the softeningtemperature and the degree of substitution, detected by ¹³C-NMRspectroscopy, of the product are indicated.

n-stearyl isocyanate Yield DS ST g/mol (g) Carbamate (° C.) 3.7/0.012510.4 0.5 220 decomposition

Comparative Reaction 5

7.1 g (0.025 mol) of plastic acetate DS 2.0 (acetate 53%) is refluxedwith 1,8-diazabicyclo[4.5.0]undec-7-ene for 30 minutes in 200 g DMAc at130° C. The isocyanate, dissolved in 50 g DMAc, is then added dropwiseand the mixture is stirred for two hours. The product is precipitatedfrom n-hexane, washed with hexane and dried.

In the table below, the amounts used, the yield, the softeningtemperature and the degree of substitution, detected by ¹³C-NMRspectroscopy, of the product are indicated.

n-stearyl isocyanate Yield DS ST g/mol (g) Carbamate (° C.) 3.7/0.01257.3 0.29 210 decomposition

What is claimed is:
 1. A thermoplasticpolysaccharide-ether/carbamate/ester derivative of the generalstructure,

wherein R is H or a substituent having a structure selected from,R=—A—B,  (i) R=—A—C,  (ii) R=—B,  (iii) R=—C, and  (iv) R=A—H  (v) inwhich A is a linear polyether chain of the following structure:A=(—D—O—)_(n) in which D denotes a linear aliphatic branched orunbranched chain of 2 to 12 C atoms, O represent an oxygen atom and n isa number equal to or greater than 1, and B represents an N-substitutedcarbamoyl of the structure

in which E denotes a linear or branched aliphatic chain of 1 to 18carbon atoms, and C represents an alkanoyl of the structure

in which F denotes a linear aliphatic, saturated or unsaturated,branched or unbranched chain of 2 to 22 C atoms, provided that saidthermoplastic polysaccharide-ether/carbamate/ester derivative containssubstituent R structures (iii), (iv) and at least one of (i) and (ii).2. A thermoplastic molding composition comprising thepolysaccharide-ether/carbamate/ester derivative of claim 1, and at leastone conventional additive selected from the group consisting ofplasticizers, impact resistance modifiers, flame retardants,anti-oxidants, UV protectors, nucleating agents and fillers.
 3. Amixture comprising: X) the thermoplasticpolysaccharide-ether/carbamate/ester derivative of claim 1; and Y) a lowmolecular weight, unbranched or branched, symmetrical or asymmetrical,aliphatic dialkyl urea derivative having chain lengths of from 1 to 20carbon atoms, wherein the molar ratio of X to Y is represented by theformula, 0.001<Y/(X+Y)<0.3.
 4. The thermoplasticpolysaccharide-ether/carbamate/ester derivative of claim 1 wherein saidthermoplastic polysaccharide-ether/carbamate/ester derivative is formedfrom the reaction of a) isocyanates or blocked isocyanates, and b)activated carboxylic acid derivatives with c) said polysaccharide ether,the thermoplastic polysaccharide-ether/carbamate/ester derivative havingan overall degree of substitution (based on the anhydroglucose unit) ofDS=0.3 to 3.0.
 5. The thermoplastic polysaccharide-ether/carbamate/esterderivative of claim 4 having an overall degree of substitution of DS=0.6to 2.8.
 6. The thermoplastic polysaccharide-ether/carbamate/esterderivative of claim 1 wherein said polysaccharide ether is a celluloseether having an average degree of substitution (MS) of 0.1 to 5, andsaid thermoplastic polysaccharide-ether/carbamate/ester derivative is acellulose-ether/carbamate/ester derivative.
 7. A method of producing acomposition comprising the thermoplasticpolysaccharide-ether/carbamate/ester derivative of claim 1 and a lowmolecular weight urea derivative, said method comprising, (a) providinga first mixture comprising said polysaccharide ether, a catalyst, asolvent and water, said polysaccharide ether being insoluble in saidsolvent, (b) forming a second mixture of apolysaccharide-ether/carbamate intermediate, said low molecular weighturea derivative and said solvent by adding an isocyanate to said firstmixture, said polysaccharide-ether/carbamate intermediate and said lowmolecular weight urea derivative being soluble in said solvent, (c)adding an activated carboxylic acid derivative to said second mixture,thereby forming said composition comprising thepolysaccharide-ether/carbamate/ester derivative of claim 1 and said lowmolecular weight urea derivative, and (d) optionally isolating saidcomposition comprising the polysaccharide-ether/carbamate/esterderivative of claim 1 and said low molecular weight urea derivative.